1) I use a ball machine. I position it 12-15 feet behind the baseline near one of the sidelines, set it for as much topspin as possible, the set the speed and height so that the balls land in the service box.

2) I hire one of our pros to hit serves to me for an hour

3) I get a hitting partner to hit serves to me

4) I get anyone to hit serves to me from the service line rather than the baseline. Even a poor server will give you a major challenge from that close.